Returns #t if the kth bit is 1; otherwise returns
#f. K must be a valid index of bit-string.

— procedure: bit-string-set! bit-string k

Sets the kth bit in bit-string to 1 and returns an
unspecified value. K must be a valid index of bit-string.

— procedure: bit-string-clear! bit-string k

Sets the kth bit in bit-string to 0 and returns an
unspecified value. K must be a valid index of bit-string.

— procedure: bit-substring-find-next-set-bit bit-string start end

Returns the index of the first occurrence of a set bit in the substring
of bit-string from start (inclusive) to end
(exclusive). If none of the bits in the substring are set #f is
returned. The index returned is relative to the whole bit string, not
substring.

The following procedure uses bit-substring-find-next-set-bit to
find all the set bits and display their indexes: